Electronic circuit boards for supporting and connecting electronic components are commonly produced using etching techniques that remove conductive material such as a continuous layer of copper foil adhered to an insulating layer in regions where connections are not desired, leaving traces of continuous conductive foil where desired between circuit nodes. Substantial amounts of the original conductive foil are commonly removed from the initial laminate of continuous conductive foil to produce the desired circuit traces in this manner.
Recent developments in polymers that are heavily loaded with metllic silver particles facilitate the fabrication of circuit boards permitting extrusion of the desired circuit traces on an insulating layer directly in the desired circuit traces. Such polymers are conductive and may be extruded along paths that are determined according to computer-controlled movements of coordinated stages to `write` the circuit traces between circuit nodes on an insulating layer. Polymers commonly used for this purpose typically rely upon multiple-solvent chemistry to provide quickly-setting conductive traces that can then be overcoated with insulative materials to promote additional extrusions of circuit traces that intersect, but do not connect to, the initially-extruded circuit traces. Complex circuit traces formed and initially set in this manner then require complete curing, for example, by baking at elevated temperatures in an oven, in order to fully cure the circuit traces in place on the insulating layer. One disadvantage of such systems is that the polymers expand as temperature increases, causing expansion of the volume of the viscous composition contained within an extruding vessel. Expansion of the composition within the extruding vessel commonly causes dribbling of the composition from an extruding tip which, when deposited on an insulating layer at the start of a conductive trace, can produce an unsightly, anomalous trace configuration that may undesirably overlap and connect to adjacent circuit traces.